Radio or like receiver



Nov. 1, 1938. A, w, EDWARDS 2,134,913

RADIO OR LIKE RECEIVER Filed Dec. 4, 1936 5 Sheets-Sheet l Nov. 1, 1938.A. w. EDWARDS 2,134,913

RADIO OR LIKE RECEIVER I Filed Dec. 4, 1936 5 Sheets-Sheet 2 Nov. 1,1938. A. w. EDWARDS 2,134,913

RADIO OR LIKE RECEIVER Filed Dec 4', 1956 5 Sheets-Sheet 3 Patented Nov.1, 1938 UNITED STATES PATENT OFFICE assignor to Ferranti N. Y.

Electric Inc., New York,

Application December 4, 1936, Serial No. 114,272 In Great BritainDecember 7, 1935 6 Claims.

This invention relates to radio or like receivers of the typeincorporating one or more band-pass filter stages such as, for instance,an intermediate frequency stage of a superheterodyne receiver.

In receivers of this type, the wider the fre quency band passed throughthe receiver, the better is the fidelity of the reproduction to thetransmission being received. In order to permit the passage of a widefrequency band the response curve of each band-pass filter stage shouldbe of the double hump form; the width of frequency band that can bepassed for any given transmission being received differs according tothe strength of the transmission, and consequently the shape of theresponse curve also differs. It is well known that tuning of receiversunder conditions of a wide response curve is difficult owing to therebeing a number of positions of the tuning apparatus for which apparentlysimilar results are obtained.

It is desirable therefore to narrow the frequency band passed throughthe receiver to correspond with a response curve having a single peakbefore performing the tuning operation, after which process the bandWidth passed is increased to suit the transmission being received.

To effect this procedure it has been proposed to provide manual meansfor ensuring that before the receiver can be tuned to the required transmission and the coupling between the coils then increased in order towiden the frequency band passed through the receiver, the couplingbetween the two members of each band-pass filter stage must bedecreased, with the result that the response curve of the filter iscaused to be of the single peak form.

The object of this invention is to provide improved or simplified meansfor achieving such result.

The invention consists in a radio or like receiver incorporatingfeatures set out in the claims appended hereto.

Referring to the accompanying diagrammatic drawings:

Figure 1 is a perspective view of part of a tuning apparatus embodyingthe present invention in one form.

Figure 2 is an enlarged side view of the intermediate frequencytransformer coils and mounting thereof with part of the enclosing casebroken away.

Figures 3 and 4 are enlarged end views of part of the tuning andfidelity control mechanism.

of the mechanism.

Figure 6 is an enlarged side View of part of the coil operatingmechanism.

Figure 7 is an enlarged end view of said part of the coil operatingmechanism, and

Figure 8 is an enlarged plan view of said part of the coil operatingmechanism.

In carrying the invention into effect according to the form illustratedby way of example as applied to a superheterodyne radio receiver, Iconstruct the intermediate frequency transformer in such a manner as tohave its two coils a, b mount-- ed coaxially, the coil or being fixedrigidly to a tubular member 0 and the coil 12 being mounted upon asleeve 0 capable of movement in an axial direction along the tube 0.

A tube 1 is slidable within the tube 0 and carries a radial pin g bywhich the tubes d and f are constrained to move together as one in avertical direction; vertical slots 72. in the tube 0 through which thepin g passes are provided to present this vertical movement. A crankedrod e is pivoted to the tube and to a slotted plate 7' and is carried infixed forks 76 whereby rotation of a shaft carrying an arm q with a pinm engaging the slot 11 in the plate 9' effects a rise or fall 1 of thecoil b. The shaft t is coupled to a shaft 0 passing through the front ofthe cabinet (not shown) containing the receiver, a knob p being attachedto the shaft 0.

Associated with the shaft 0 is a fidelity control device which comprisesa notched wheel r mounted frictionally on the shaft, being held by meansof a spring washer or the like (not shown). The degree of friction issuch that when the notched wheel 1" is held, a spring u tending torotate the shaft t in a counterclockwise direction in Figures 3 and 4 isunable to rotate the shaft.

Two pins or fingers v, 12 attached rigidly to or forming part of thelower ends of two approximately diametrically opposite arms w, a:co-operate with the notched wheel r in such a manner that when one pinor finger v, o is in engagement with the wheel 1", the other bearsagainst the periphery of the wheel between two adjacent notches. The twoarms to, a: are pivoted to each other at the mid-point of each. A cam sis provided in driving relationship with the shaft and adjacent to thenotched wheel 1'; this cam has two approximately diametrically oppositelifts 50 y, z, the lift 2 being provided with a stop 2 at the topthereof. The fingers follow the cam whenever the latter rotates, ridingup the lifts until the stop prevents further rotation of the cam. Asubsidiary spring 3 is disposed on the pivot 4- Lit) Til

between the two arms so as to urge both fingers v, 22' towards thenotched wheel r.

The tuning apparatus includes a spindle 5 which latter is mountedparallel to the shaft 0. A star wheel 6 is fixed rigidly on thisspindle. Two studs 1, 8, one attached to each of the remote ends of thetwo arms referred to above, cooperate with the star wheel 6 in such amanner that in the position shown in Figure 3 the arm 23 engaged by thefinger v with the notched wheel r is also engaged by a stud with thestar wheel 6, the other arm 20 being held out of engagement with thenotched wheel 1' by the pin 8 engaging the star wheel 6.

In operation, assuming the receiver to have been tuned to a particularstation and the cou pling between the coils a, b of the intermediatefrequency transformer to have been adjusted to give a response curvesuited to the station in question; upon rotating the tuning spindle 5,with the object of effecting a change in the station being received, thestar wheel 5 rotates therewith and on the first movement the pin 1 whichis in engage ment with it is forced outwards so that the finger v on theopposite end of the arm at to which the pin 7 is attached is lifted outof engagement with the notched wheel r. Thus the notched wheel is nolonger held and the spring it causes the shafts t, o to rotate into theposition shown in Figure l and the movable coil b of the intermediatefrequency transformer to move towards its lowermost position.

The cam s on the shaft rotates with the shaft sufficiently for the twoswell portions 1/, z to lift and retain the two fingers o, 2; out ofcontact with the notched wheel r, thus simultaneously preventing thepins 7, 8 on the opposite ends of the arms from contacting orre-engaging with the star wheel 6.

The mechanism now occupies the position shown in Figure 4. The tuningspindle is now free to be rotated without actuating the arms 10, m andit may be adjusted into any desired position.

When the receiver has been retuned to the desired station, the operatorturns the knob 11 attached to the shaft 0 in order to move the movablecoil 73 nearer to the fixed coil it until the coupling is such as togive a response curve suited to the new station. This operation rotatesthe cam s in clockwise direction and allows the fingers to drop from theswells or lifts of the cam to contact with the notched wheel 1', e. g.as shown in Figure 3. I

As soon as one or other of the two fingers engages with the notchedwheel the latter is arrested and the pins 1, 8 are brought intooperative engagement with the star wheel 6 ready for the next retuningprocess, but the knob p may be moved to vary as desired the position ofthe moving coil 21 since the notched wheel r remains locked.

The teeth of the notched wheel 1" are so shaped as to ensure that one orother finger v, 12 will drop into a notch.

The stop 2 on the cam 8 may be employed as an audible indicating device,the sound caused When it strikes the finger 2i acting as an indicationto. the operator that the receiver is in its high selectivity condition.

The arrangement described for enabling rotation of the shafts to effectmovement of the coil on the intermediate frequency transformer is by wayof example only and does not form part of the invention.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is 1. A receiver incorporating an adjustablebandpass filter circuit, a tuning control device, means actuated by mererotation for tuning purposes of said tuning control device automaticallyreducing to a pre-set minimum the frequency range of responsiveness ofsaid band-pass filter circuit and a further control device forsubsequently increasing to any desired extent the frequency range ofresponse.

2. A receiver as claimed in claim 1 wherein the said band-pass filtercircuit includes relatively movable members for varying the degree ofcoupling and in addition there is provided as part of said meansactuated by mere rotation of said tuning control device a return springfor urging the said members to adopt a position corresponding to minimumfrequency range of responsiveness of said band-pass filter circuit,retaining means for preventing the said members from responding to theaction of the said return spring and further means associated with saidtuning control device operable to release said retaining means uponvariation of the position of said tuning control device.

3. A receiver as claimed in claim 1 wherein the said band-pass filtercircuit includes relatively movable members for varying the degree ofcoupling, there is provided as part of said means actuated by mererotation of said tuning control device a return spring for urging saidmembers to adopt a position corresponding to minimum frequency range ofresponsiveness of said band-pass filter circuit, retaining means forpreventing the said members from responding to the action of said returnspring, and further means associated with said tuning control deviceoperable to release said retaining means upon variation of the positionof said tuning control device and wherein said retaining means include anotched wheel mounted frictionally on a shaft operatively associatedwith said relatively movable members and two arms are provided having afinger on one end of each arm, the fingers being urged into engagementwith said notched wheel by the action of a subsidiary spring, thearrangement being such that when one of the pins engages a notch theother contacts with a tooth.

4. A receiver as claimed in claim 1 having relatively movable membersfor varying the degree of coupling in said band-pass filter circuit andwherein said means actuated by mere rotation of said tuning controldevice include a return spring for said members, retaining means forsaid members, releasing means for said retaining means operable by saidtuning control device, said retaining means including a notched wheelmounted frictionally on a shaft operatively associated with saidrelatively movable members, two arms having a finger on one end of each,the fingers being urged into engagement with said notched wheel by asubsidiary spring, said releasing means associated with said tuningcontrol device serving to release a finger from engagement with saidnotched wheel, and a cam serving to prevent engagement or re-engagementbetween the fingers and the notched wheel upon rotation of said shafthaving been effected by said return spring.

5. A receiver as claimed in claim 1 including as part of said meansactuated by mere rotation of said tuning control device a cam, a pair ofarms having fingers at both ends of each, a

notched wheel associated with one pair of fingers, a star wheelassociated with the other pair of fingers, a cam associated with saidnotched wheel, a part on said cam co-operating with a stop and a returnspring for urging said part of the cam into engagement with the stop.

6. A receiver including in combination an adjustable band-pass filtercircuit having two relatively movable members for varying the degree ofcoupling, a return spring for urging said members into a positioncorresponding to minimum frequency range of responsiveness of saidband-pass filter circuit, a tuning control device, a

fidelity control shaft associated with said relatively movable members,a. notched wheel on said shaft, a star wheel associated with said tuningcontrol device, a pair of arms having fingers on both ends of each, thefingers on the opposite ends of one arm simultaneously respectivelylying between a pair of teeth on the star wheel and engaging a notch inthe notched wheel whilst the fingers on the opposite ends of the otherarm simultaneously respectively rest upon the extremity of a star wheeltooth and a notched wheel tooth.

ARTHUR WALLACE EDWARDS.

